1. Field of the Invention
This invention relates to a zoom lens with a close-up lens which is used in an enlarger or the like, and more particularly to a conjugate distance variable zoom lens with a close-up lens disposed on the light measuring system side of a prism which splits light bundle transmitted through a negative film into light bundles traveling toward a printing system and a light measuring system.
2. Description of the Prior Art
As a color printer for printing a color negative image on a color photographic paper, there has been known one in which light bundle transmitted through a negative film bearing thereon the negative image is led to a light measuring system by a mirror or the like and the pattern, density, color and the like of the color negative image are inspected by a scanner and the intensity of light and color balance of light to be given to a color photographic paper are automatically controlled on the basis of the result of the inspection.
There are various negative films such as Disc film, 135 film, 120 rollfilm and the like which are different in size. Accordingly, when printing an image on a color photographic paper, the printing lens must be changed according to the size of the negative film and at the same time, the scanner lens must be changed or the magnification of the scanner lens must be changed.
Generally the magnification of the scanner lens is manually changed, which can lead to wrong setting of the magnification. In order to avoid such a problem, there has been proposed a system in which the magnification of the scanner lens is automatically changed in response to change of the printing lens.
Since, in such a printer, the print lens is disposed just above the negative film, the scanner lens must inspect the negative film obliquely or by way of a mirror. However, to obliquely mount the scanner lens is more difficult than to mount it vertically or horizontally, and when the mirror is moved in and out each time the negative film is inspected, the number of prints per unit time is reduced.
There has been proposed an optical system in which a split prism is connected to print lenses which are for a small negative film and are frequently used and the light measurement is effected through the prism while in the case of print lenses which are for a large negative film and are used less frequently, the light measurement is effected through a mirror taking into account the cost of a prism.
However such an optical system gives rise to a problem that the conjugate length for a given magnification of the scanner lens changes depending on the presence of absence of the prism. In conventional scanner lenses, focusing of the scanner lens in response to change in the conjugate length results in change of the magnification and deterioration of the lens performance.